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Cerebellum

CerebellarSigns

Key Cerebellar Functions

• Comparison of intent and action (ie., errors) and generates corrective signals

• Motor learning and adaptation• Motor cognition and general cognition

(new evidence; controversial)

• Plays a role in automating and optimizing behavior

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Lecture Plan:

• Structural and functional overview• Principal pathways into and out of the

cerebellum• Experimental approaches to reveal:

– Anticipatory control– Motor learning– Mental processes underlying movement

control

Motor Hierarchy

Exerts influenceat all levels

Intent

Actual

1° Som sensory

Cerebellar Functional Anatomy

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Folia

Cerebellar Cortex

Deep Cerebellar Nuclei:Dentate

InterposedFastigial

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Input-output Organization

Cerebellarcortex

FastigialInterposedDendate

Deep CerebellarNuclei:

Vestibularnuclei

Cortex

Nuclei

Output

Extrinsic inputs: mossy fiberclimbing fiber

+-

+

+

CerebellarDivisions

IVth vent VermisIntermediate hem.

Spinocerebellum:Vermis

Intermediate hem.SpinocerebellumSpinocerebellum((VermisVermis + + IntermedIntermed. Hem). Hem)

Control of limbs and trunk

Lateral hem.

Cerebrocerebellum:Lateral hem.

Cerebrocerebellum(Lateral hemisphere)

Planning of movement+

Floculo-nodular lobe

Vestibulo-cerebellum(Floculo-nodular lobe)

Control of eye & head movements

Balance

Nissl-stained section through cerebellar cortex

Molecular layer

Purkinje layer

Granular layer

White matter

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Cerebellar CortexInputs

Output

Interneurons

Climbing fibersMossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neuronsGolgi neurons

Purkinjeneuron

Apicaldendrites

Cellbody

Cerebellar CortexInputs

Output

Interneurons

Climbing fibersMossy fibers

Purkinje neurons

Stellate neurons -Granule neurons +

Basket neurons -Golgi neurons -

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Cerebellar Cortex: activation by mossy fibers

Inputs

Output

Interneurons

Climbing fibersMossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neuronsGolgi neurons

to Deep CerebellarNuclei

+-

Cerebellar Cortex: activation by climbing fibers

Inputs

Output

Interneurons

Climbing fibersMossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neuronsGolgi neurons

to Deep Cerebellar Nuclei

+-

Inferior olivary nucleus: source of all climbing fibers

to cerebellum,via inferior peduncle

Mossy fibers from all other sources

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Cerebellar Cortex: Inhibitoryinterneurons

Inputs

Output

Interneurons

Climbing fibersMossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neuronsGolgi neurons

Functional divisions

VermisIntermediate hem

CerebrocerebellumLateral hemisphere

Spinocerebellum

Vestibulo-cerebellumFloculo-nodularlobe

CerebrocerebellumLateral hemisphere

Dentate

Intermediatehemisphere

Interposed

To lateralsysetms

Spinocerebellum

Vermis

Fastigial

To medialsysetms

To frontalmotor areas

Motorplanning

Motorexecution

Vestibulo-cerebellum

To vestibular nuclei

Eye mvt &balance

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Medial & lateral systems

Interposednuclei

Fastigial

Vestibulocerebellumvia vestibular nuclei

Intermediate and LateralHemispheres

Cerebellar cortex & Deep nuclei

Brain stem nuclei

Thalamus and Cortical motor areas

Ipsilateral

Planning andlimb control

Intermediate and LateralHemispheres

Vermis & Vestibulocerebellum

BilateralIpsilateral

Cerebellar cortex & Deep nuclei

Brain stem nucleiAxial control

Thalamus and Cortical motor areas

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Functions of the Cerebellum

• Feed- forward or predictive motor control (nuts & bolts of skillful movements)

• Motor learning/adaptation• Non- motor functions:

– Active tactile exploration– Higher brain functions (cerebellar cognitive-

affective syndrome)

Anticipatory control• Anticipating the motor consequences of an event

– See stop light and brake– Predict baseball location during batting– Anticipating duck location in an video game

• Cerebellum’s role:– Fairly low level routines– Correlations & associations

• Implemented via lateral and medial pathways

Feed-Forward or Predictive Control

Normal:• Perturbation extends arm,

stretching biceps• Muscle action flexes arm and

tends to restore arm position• Anticipatory contraction of

triceps (extensor) prevents flexion overshoot– Occurs during triceps

shortening; not stretch reflex– BRAKE

• Result: arm position stabilized at start position

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Feed-Forward or Predictive Control

Block cerebellar function (cool):• Perturbation extends arm,

stretching biceps• Biceps contraction prolonged• Muscle action flexes arm but

well beyond initial arm position--OVERSHOOT

• Delayed triceps contraction– Reverts to simple stretch reflex– LOSS of brake (antic. control)

• Result: cycle of flexion-extension (similar to cerebellar tremor)

Feed-Forward or Predictive Control

Delayed triceps (antagonist)produces oscillations

MotorLearning

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Non-motor FunctionPassive stimulation Discriminate roughness

Manipulate only Manipulate + discriminate

Cerebellar Motor Functions

• Implemented via lateral and medial pathways, especially the corticospinal tract

• Incorporated into motor programs via frontal motor areas (SMA, premotor cortex…)

• Becomes part of motor strategy via prefrontal cortex

Lateralcerebellum

MD

Intermediatecerebellum

Premotorcortex

1° motor cortex

VA/VL

Planningmovements

Executingmovements

Dorsolateral prefrontal cortex

Movement strategiesWorking memory

All work togetherduring a motor task:-anticipatory control duringmotor learning

-using sensory informationto guide movement

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Cerebellar Cognitive Affective Disorder

• Lesions of the posterior lobe and vermis• Impairment of executive functions

– Planning, verbal fluency, abstract reasoning• Difficulties with spatial cognition

– Visuo-spatial organization, visual memory• Personality changes

– Blunting of affect, inappropriate behaviors• Language disorders

– Agrammatism

Lateralcerebellum

MD

Dorsolateral prefrontal cortex

Cognition

Anterior cingulate cortex Emotions/affect

Conclusions

• Cerebellar lesions produce– Incoordination & errors not weakness– Lose ability to anticipate errors– Lose ability to correct

• Motor learning• Not just motor